The principles and applications of time‐of‐flight mass spectrometry involving instruments with independent (orthogonal) axes for ion generation and mass analysis are reviewed. This approach, generally referred to as orthogonal acceleration time‐of‐flight mass spectrometry, has proved particularly advantageous for the combination of continuous ionization sources with time‐of‐flight mass spectrometry. The history of the technique is briefly discussed along with the instrumental principles pertaining to all the stages of the instrumentation from ion source to detector. The applications of commercial and customized instruments are discussed for several ionization methods including electrospray, matrix assisted laser desorption/ionization, electron ionization, and plasma ionization. © 2000 John Wiley & Sons, Inc., Mass Spec Rev 19: 65–107, 2000

In the 1990s time-of-flight mass spectrometry (TOFMS) has reestablished itself as a mainstream technique in mass spectrometry. There have been several developments which have contributed to this. The development of the technique of matrix-assisted laser desorption/ionization (MALDI), a pulsed ionization method, has provided a user-friendly, low-cost window on the high mass regime for the molecular biologist. The availability of high-speed computers has allowed efficient processing of TOF data on the microsecond time-scale. The emergence of practical ion optical approaches for space, time and velocity focusing have improved the resolving power and sensitivity of TOFMS far beyond its limited performance in previous decades. The technique of time-of-flight mass spectrometry (TOFMS) has returned as a prominent mass analysis method. TOFMS can be advantageous compared to scanning technologies because of its 'unlimited' mass range, high speed and the potential for high duty factors (% of ions formed that are detected). Two important causes for the renewed activity in TOFMS can be identified: (i) The development of and need for new ionization methods capable of generating ions of structural significance from high molecular weight materials. In particular, developments in ion sources for molecular biology provide a strong driving force for TOFMS. Matrix-assisted laser desorption/ionization (MALDI) 1 and electrospray ionization (ESI) 2 have been prominent in this regard. (ii) The facilitating technologies for TOFMS have advanced dramatically during the past decade. These include affordable pulsed lasers, nanosecond digitizers, focal plane detectors and microcomputing power.The convergence of the need for high mass analysis with the availability of the necessary technology has been perfectly timed. But the recent successes of TOFMS must equally be attributed to research directed at overcoming the physical limitations inherent in the TOFMS experiment. Dispersions in the initial position, time and velocity of the ion population severely limited the resolving power of early TOFMS instruments. Inefficient production, gating and detection of ion packets have, until recently, placed considerable constraints on the sensitivity of the TOF mass analyser. The need to form discrete packets of ions has provided a challenge in the coupling of continuous ion sources to TOFMS.The development of the ion mirror (or reflectron) 3 and the orthogonal acceleration time-of-flight mass spectrometer (oa-TOFMS) 4-6 have been key stages in the revival of TOFMS. FACTORS CONTRIBUTING TO TOFMS RENAISSANCEThe simplicity of the physical principles of TOFMS underpin its current successes. The mass-velocity relationship for constant energy ions and the electrostatic force on a charge when combined with Newtonian mechanics provide the foundations of all TOFMS equations:force on a charge in an electric field F = ma Newton's second law a = Eq/m acceleration in a constant electric field where q = charge; V = electrical potential through which an ion having ch...

CO2 laser ablation of the frozen water matrix, followed by resonance-enhanced multiphoton ionization technique coupled with reflection time-of-flight mass spectrometry, has been used for analysis of water polluted with phenol molecules. The linear dependence of the ion signal on the phenol concentration ranged from 0.1 fig L-1 to 10 mg L-1 under identical experimental conditions. A detection limit of 0.1 fig L-1 was achieved for phenol. It was shown that the overall sensitivity of 1 ng L-1 (1 ppt) can be attained with the present experimental setup. The velocity distribution of the ablated phenol species was approximated by a Maxwell-like function at a temperature

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